Retouching is a term commonly applied to a post processing step in photographic film development wherein a film image, for example a color negative film image or a reversal type film image, is treated to proportionally remove and/or reduce the intensity of the dyes therein. In the development of photographic images, a color film transparency is frequently prepared. The film transparency permits some alteration in color or tone, i.e., retouching. Additionally, dye transfers which are continuous tone prints printed in magenta, cyan and yellow can be used for retouching when more work is required than can be done on a transparency or when the transparency is not sufficiently large to permit sufficient working thereon. In the retouching process, it may be necessary to remove entirely, or at least to reduce the intensity of, one or more of the three colors. Various chemical substances are available which act as solvents for one or more of the dyes. Various chemical compositions and combinations are also available which attempt to remove or reduce the intensity of all three dyes. Generally, retouching involving the chemical process of reducing the cyan, magenta and yellowed dye sets in an overall neutral manner to their leuco or uncolored form is often desirable.
Patent defensive publication No. T 883,013 discloses the use of a mixture of a 5-pyrazolone coupler and a naphthol sulfonic acid to uncouple cyan dye and form a soluble dye which can be washed out of the film. Defensive publication T 896,053 discloses, for the same purpose, the use of an iodine and potassium iodide solution, followed by treatment with ammonium thiosulfate. The Anderson U.S. Pat. No. 4,370,402 discloses aqueous compositions for removing or reducing the intensity of dyes in dye transfers. The composition comprises a thiourea and an ammonium nitrate compound.
Many prior art retouching compositions are directed to reducing the intensity of only one or two dye colors, or provide only limited success in the overall bleaching or retouching of filmed images. Accordingly, there is a continuing need for improved retouching compositions and methods for use in the photographic art.